Truth is, all the numbers related with average calculations are reset. Thus the first ranked score played will be the first new average. It's up to you if it's lower or higher than before :)
Another truth is that the game becomes more difficult with each new tier, be it longer tees or faster greens. Therefore the scores may easily go up a bit and the average will follow.
Tour Masters play on (slower) Tournament greens opposed to the Very Fast greens of Masters. Hit it with caution, have fun!